Estimating a subscriber location

• US 20110021210A1
• Filed: 07/23/2009
• Published: 01/27/2011
• Est. Priority Date: 07/23/2009
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Medapalli, Kameswara, Lorenz, Robert G., Hochwald, Bertrand, Paulraj, Arogyaswami
• Granted Patent: US 8,290,508 B2
• Time in Patent Office: Days
• US Class Current: 455/456.2
• CPC Class Codes: G01S 5/0244 Accuracy or reliability of position solution or of measurements contributing thereto
• CPC Class Codes: G01S 5/14 Determining absolute distances from a plurality of spaced points of known location
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

A method and apparatus of estimating a location of a subscriber are disclosed. One method includes receiving a request for the location of the subscriber. The subscriber'"'"'s serving base station, and a plurality of neighboring base stations sensed by the subscriber, are identified. At least two of the neighboring base stations are selected to aid in estimating the location of the subscriber. Stored locations of the serving base station and the selected neighboring base stations are accessed. The subscriber obtains a time delay from the serving base station for maintaining synchronization of the subscriber with the serving base station. The subscriber estimates a distance between the subscriber and the serving base station based on the time delay. The subscriber receives frames including preambles from each of the selected neighboring base stations, and estimates a delta time for each of the selected neighboring base stations for the subscriber to synchronize to each of the selected neighboring base stations. The subscriber estimates distances between the subscriber and each of the selected neighboring base stations based on the time delay and the delta time of each of the selected neighboring base stations. The subscriber location is estimated by trilateration of the distance between the subscriber and the serving base station, and the distances between the subscriber and each of the selected neighboring base stations.

Claims

1. A method of estimating a location of a subscriber, comprising:

receiving a request for the location of the subscriber;

identifying the subscriber'"'"'s serving base station, and a plurality of neighboring base stations sensed by the subscriber;

selecting at least two of the neighboring base stations to aid in estimating the location of the subscriber;

accessing stored locations of the serving base station and the selected neighboring base stations;

the subscriber obtaining a time delay from the serving base station for maintaining synchronization of the subscriber with the serving base station;

the subscriber estimating a distance between the subscriber and the serving base station based on the time delay;

the subscriber receiving frames comprising preambles from each of the selected neighboring base stations, and estimating a delta time for each of the selected neighboring base stations for the subscriber to synchronize to each of the selected neighboring base stations;

the subscriber estimating distances between the subscriber and each of the selected neighboring base stations based on the time delay and the delta time of each of the selected neighboring base stations;

estimating the subscriber location by trilateration of the distance between the subscriber and the serving base station, and the distances between the subscriber and each of the selected neighboring base stations.

2. The method of claim 1, wherein selecting at least two of the neighboring base stations comprises determining the at least two neighboring base stations having the largest received signal power at the subscriber.

3. The method of claim 1, wherein selecting at least two of the neighboring base stations comprises analyzing a relative physical orientation of the neighboring base stations and the serving base station and selecting the at least two neighboring base stations that along with the serving base station provide a non-collinear spatial distribution about the subscriber.

4. The method of claim 1, wherein a subscriber scan of neighboring base stations is initiated if a scan has not been performed in greater than a threshold amount of time.

5. The method of claim 1, wherein identifying neighboring base stations comprises the subscriber scanning for a potential subscriber handoff base stations, pruning sector information from the scan, yielding the neighboring base stations.

6. The method of claim 1, wherein the subscriber obtaining a time delay from the serving base station for maintaining synchronization of the subscriber with the serving base station comprises:

estimating a time of arrival of a serving base station signal comprising extracting information from a downlink frame preamble;

obtaining the time delay based on the estimated time of arrival.

7. The method of claim 6, wherein extracting information from a downlink frame preamble comprises:

determining a channel impulse response of the preamble;

estimating the time of arrival by comparing a peak of the channel impulse response with a pre-estimated start time of the downlink frame preamble.

8. The method of claim 7, wherein determining a channel impulse response of the preamble comprises:

performing an fast fourier transform (FFT) on the downlink frame preamble;

correlating an output of the FFT with a predetermined pseudo random bit sequence (PRBS);

performing an inverse fast fourier transform (IFFT) on the correlated output.

9. The method of claim 1, wherein the subscriber obtaining a time delay from the serving base station for maintaining synchronization of the subscriber with the serving base station comprises:

the subscriber transmitting a signal to the serving base station within an unscheduled portion of an uplink sub-frame, having a time offset of zero;

the serving base station receiving the signal, and estimating the time delay required for the subscriber to align subscriber transmissions to a start time of the unscheduled portion of the uplink sub-frame;

the serving base station communicating the time delay to the subscriber;

the subscriber estimating a transmission delay between the subscriber and the serving base station as being equivalent to the time delay.

10. The method of claim 9, further comprising the serving base station averaging the time delay over multiple frames before communicating the time delay to the subscriber.

11. The method of claim 1, wherein estimating a delta time for each of the selected neighboring base stations for the subscriber to synchronize to each of the selected neighboring base stations comprises:

based on preambles of wireless signal frames received from each of the selected neighboring base stations, the subscriber estimating the delta time that required to synchronize the subscriber with each of the selected neighboring base stations;

the subscriber estimating a transmission delay between the subscriber and each of the selected neighboring base stations based on the time delay and the delta time of each of the selected neighboring base stations.

12. The method of claim 11, further comprising the subscriber averaging the delta time of each of the selected neighboring base stations, over multiple frames.

13. The method of claim 1, wherein the subscriber comprises a host and a mobile device.

14. The method of claim 13, wherein the host generates the request for the subscriber'"'"'s location, and accesses the stored locations of the serving base station and the selected neighboring base stations.

15. The method of claim 13, wherein the mobile device identifies the subscriber'"'"'s serving base station and the plurality of neighboring base stations sensed by the subscriber, selects at least two of the neighboring base stations to aid in estimating the location of the subscriber, obtains the time delay from the serving base station for maintaining synchronization of the subscriber with the serving base station, estimates the distance between the subscriber and the serving base station based on the time delay, receives frames comprising preambles from each of the selected neighboring base stations, and estimates the delta time for each of the selected neighboring base stations for the subscriber to synchronize to each of the selected neighboring base stations, estimates distances between the subscriber and each of the selected neighboring base stations based on the time delay and the delta time of each of the selected neighboring base stations, estimates the subscriber location by triangulating the distance between the subscriber and the serving base station, and the distances between the subscriber and each of the selected neighboring base stations.

16. A method of estimating a location of a subscriber, comprising:

identifying the subscriber'"'"'s serving base station, and a plurality of neighboring base stations sensed by the subscriber;

selecting neighboring base stations to aid in estimating the location of the subscriber;

accessing stored locations of the serving base station and the selected neighboring base stations;

the subscriber obtaining a time delay from the serving base station for maintaining synchronization of the subscriber with the serving base station;

the subscriber estimating a distance between the subscriber and the serving base station based on the time delay;

the subscriber receiving frames comprising preambles from each of the selected neighboring base stations, and estimating a delta time for each of the selected neighboring base stations for the subscriber to synchronize to each of the selected neighboring base stations;

the subscriber estimating distances between the subscriber and each of the selected neighboring base stations based on the time delay and the delta time of each of the selected neighboring base stations;

estimating the subscriber location by triangulating the distance between the subscriber and the serving base station, and the distances between the subscriber and each of the selected neighboring base stations.

17. A method of a mobile device estimating a location, comprising:

identifying a serving base station, and a plurality of sensed neighboring base stations;

selecting at least two of the neighboring base stations to aid in estimating the location;

obtaining a time delay from the serving base station for maintaining synchronization with the serving base station;

estimating a distance between the mobile device and the serving base station based on the time delay;

receiving frames comprising preambles from each of the selected neighboring base stations, and estimating a delta time for each of the selected neighboring base stations for the mobile device to synchronize to each of the selected neighboring base stations;

estimating distances between the mobile device and each of the selected neighboring base stations based on the time delay and the delta time of each of the selected neighboring base stations;

estimating the location by triangulating the distance between the mobile device and the serving base station, and the distances between the mobile devices and each of the selected neighboring base stations.